1. Field of the Invention
The invention relates to an automatic film threading apparatus for photographic apparatus.
2. Description of the Prior Art
Automatic film threading devices are known are generally include a rotary member adapted to cooperate with the outer convolution of a roll of film or strip to rotate the whole roll. During this operation, a stripper member is adapted to separate the free end of said outer convolution so as to direct it along a threading path.
A disadvantage of this type of arrangement lies in the problem of controlling the pressure of the stripping member within a prescribed range and preventing it from exerting too great a pressure on the film which can cause premature wear or even damage to the film. On the other hand, it should be appreciated that too low a pressure between the stripping member and the film could allow the leading end of the film to pass between the stripping member and the next convolution of wound film instead of being guided in the desired direction.
In addition, thin film less than 3 mils in thickness is difficult to handle. Such film has a tendency to adhere to the adjacent convolution of film, thereby making it considerably more difficult for a stripping member to separate the leading end portion of the film from the film roll. The presence of static electricity and/or dirt particles also aggravates the problem by causing the film to cling to the walls of the magazine or reel. As a result of such clinging action, there exists a greater likelihood that film damage may occur as well as many aggravating film jams.
Reliability is another area where problems have existed in the prior art for quite some time, especially in the ability to reliably thread partially loaded spools and/or cartridges. This problem has been compounded by the fact that when a threading failure is encountered, the film is frequently damaged by folding, crinkling or bending which further reduces threading reliability associative with that film for subsequent attempts at threading.